The present invention relates to a web terminal detecting device for detecting the terminal of an ink ribbon accommodated in an ink ribbon cassette of a printer.
Ink ribbons for printers accommodated in a cassette case similar to a magnetic tape cassette are widely used. Various types of ink ribbon cassettes have been proposed in which a supply reel and a take-up reel are provided, and the leading end of the ink ribbon is fixed to the take-up reel and the terminal is fixed to the supply reel. Where both ends of the ink ribbon are respectively fixed to the supply reel and the take-up reel as described above, if the terminal of the ink ribbon is not accurately detected, the same portion of the ink ribbon will be used repeatedly for many times, and thus if the tape is of a one-time use type, the recording will become impossible, and if the tape is of a multi-time use type, the printing density will be gradually reduced. For this reason, it is required to detect the terminal of the ink ribbon to know that the ink ribbon has been used to the end, and to stop the printing or typing operation.
In order to meet such requirements, it has been known in the art to provide a light reflecting tape on the terminal of the ink ribbon, and to detect the terminal of the ink ribbon by optically sensing the light reflecting tape. For example, in U.S. Pat. No. 4,115,013, an ink ribbon terminal detecting device is disclosed in which optical detecting means having a light emitting section and a light receiving section is provided on a cassette supporting portion of a printer, and an opening for inserting the optical detecting means is formed near the exit of the ribbon of the ink ribbon cassette. A light reflecting mark is affixed to the terminal of the ink ribbon, and by detecting the light reflecting mark by the optical detecting means, the terminal of the ink ribbon is detected. In this ink ribbon terminal detecting device, however, since the optical detecting means is provided in the vicinity of the ink ribbon, if the ink ribbon is glossy, light emitted from the light emitting section and illuminating the ink ribbon will be reflected by the ink ribbon. And hence, there is a problem that if the reflected light is received by the light receiving section then a signal indicating the terminal of the ribbon will be generated.